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Why do we need to starve the engine before turning it off?
This question is for Piper Tomahawk, but I guess applies to any small aircraft.
Why do we need to use the fuel mixture to starve the engine before turning it off with the key? Why can't we just turn it off with the key like in a car?

In 15 yrs of flying I'd never even given this much thought. Good question.

Car experience only, I was always told this was to leave the cylinders dry for a easier start next time.

Just a remark: The Aquila A 210 I fly as my trainer for PPL does not have a mixture control. We actually just turn the key as you would in a car. However my flight school added to the checklist that you first turn the ignition to the right magneto only, to slow down the engine as much as possible before shutting it down entirely (at least that was what I have been told).

@geisterfurz007 The magnetos are a redundancy, the engine should still run on either, which is why the pre-flight check includes removing each in turn.  A lean mix will prevent unconsumed fuel in the system, and allow spark retardation to also prevent knock-back and dieseling.

Any recent car does that too, only without you noticing.

The reason is the large spinning thing on the front. Residual fuel in the engine has been known to auto-ignite (i.e. combust without a spark), causing the prop to spin, causing serious injuries and deaths. A lean cutoff reduces the risk that someone handling the prop will get maimed or killed.
In a car when you turn the engine off usually it is in park or neutral, so if the engine turns a few revs the car goes nowhere, even if it is in gear the car may lurch but that's generally it. Modern car engines have electronic fuel injection and electric fuel pumps, some modern push-button gasoline engines are stopped by performing a lean cut-off, turning off the injectors before the plugs, most work by just stopping ignition. Diesels don't have spark plugs, they rely on compression alone, so cutting off fuel is the only way to stop them.

In cars, this is usually called dieseling

@J... Interesting, that does go against what I was taught. A cursory search doesn't bring up any reliable sources and  don't have my books on reciprocating engines on hand, can you point me to a source? My gut feeling is that wikipedia's reasoning, while weak, is sound... after all, fuel-air explosives are a thing, right?

@AEhere Well, explosion and detonation are different - detonation is a supersonic explosion.  You can have an explosion which isn't a detonation.  With that said, I take the rest of it back.  I guess it does produce a true detonation (ie: no flame front burning progressively from an ignition point, but near spontaneous (supersonic) reaction of the entire fuel/air volume).  TIL.

Surely there is manufacturer info related to this that can be added as a citation? I think the largest reason when comparing to cars is that small airplane engines have ancient technology by comparison. There is no fuel mixture control in electronically controlled engines. Most of the cars since 70s or 80s have had what could be essentially regarded as “FADEC” in the airplane world.

@GdD you state that most car gasoline engines are stopped by performing "a lean cut-off rather than a spark."  I mostly own and have owned diesel engines,  but none of the gas engines I own or have owned on automobiles actually kill the engine by fuel starvation. In fact they keep on injecting, and just shut off the spark. Out of curiosity, can you name a few that do a lean cut-off to shutdown?  Thanks.

That's a good call @mongo, I was thinking of some of the pushbutton ignition cars I've had, but the majority do not work like that. I will edit for clarity.

@GdD, I thought you had one on me there, so I have done a little research, and the best I have found thus far is power plants which have fuel cutoff solenoids, but actually kill the engine by killing the ignition. The solenoid is used to help counteract the fuel pump, which compresses the fuel to a high pressure prior to the injectors.  It may be noteworthy that it is customary to use mags to shutdown a seaplane when docking, something I miss when flying a C208 on floats. It stops the prop faster. In the Caravan the prop can be moved towards beta if needed to stop thrust.

I want to put a prop in beta at least once some day @mongo! Seaplanes too, alas in all of the EU as far as I know there's 2 places for seaplane training, one on Lake Como, Italy and one in Scotland, neither of which are practical. I could get a rating but I'd never get to use it!

Weekend outings in a floated 208 are a bit beyond my budget. However, it is a nice workhorse option under the right circumstances.

So you can't put an airplane engine in neutral, then?

@MasonWheeler Most piston airplanes don't have a transmission at all -- the engine connects directly to the propeller. Neutral in a car basically tells the transmission to not connect the engine to the wheels. Without a transmission, there can't be a neutral.

Or conceivably a clutch that can be locked in a disengaged position. But I imagine that you probably don't want a clutch failure at altitude.

A clutch is weight and expense you don't need. What problem does it solve that isn't already fixed by using the correct shutdown procedure?

Combustion in a gasoline internal combustion engine for most aircraft, requires four things: fuel, oxygen, compression and ignition.
If the engine is starved of fuel, accidental combustion (and an accidental spinning prop) will not happen.  So shutting off the fuel is one way to prevent accidental "start" if even for one stroke.
Oxygen is ubiquitous and is not practical to eliminate from the engine environment.
Compression can happen when someone intentionally or unintentionally moves the prop, which coupled to the crankshaft may cause a cylinder to go through a compression stroke.  Since frequently props are moved to place cowl plugs, attach tow bars, etc. the risk of a partially rotating prop is non-zero.
Ignition happens in many forms.  Hot carbon deposits, hot spark plugs, nicks in pistons are all sources of continued ignition when trying to shut down an engine. Removing fuel eliminates these sources of ignition from causing continued rotation of the engine.
The most significant source of ignition in most aircraft gasoline engines is the magnetos which are used to energize the spark plugs.  Magnetos are effective at creating energy even at low rotational velocities.  Many aircraft engines also have "impulse" magnetos, which are spring loaded, and trigger on a very low rotational velocity.  They have the advantage of being effective starting aids.  Furthermore, magnetos, while switchable, are normally "grounded" to disable them. There is significant history that broken or intermittent magneto switches, broken or intermittent wires and other causes are responsible for unintended engine starts or undesired engine firings.
To relate a story which happened at a local airport several years ago.  A ferry pilot brought a plane to town at night, tied it down at the rural airport, and was to meet the prospective buyer the next morning.  The buyer arrived at the strip early the next morning, and while waiting for the ferry pilot, poked around the locked plane.  Eventually something possessed him to rotate the prop through manually. Normally that would not have been a problem, except the magneto switch in the aircraft was "open" in the off position, which meant that both magnetos were hot.  This was likely not noticed because not everyone does a magneto "ground" check in the off position during their run-up process.  However, if the mixture idle-cutoff were in the cutoff position, there would not be fuel available in the carburetor to ignite, except for some reason (such as the ferry pilot extracting his RON bag in the dark) the mixture was nearly full rich. Normally this might have resulted in the engine firing, or even starting and idling. Again, this morning, things were not normal.  The RON bag, extracted in darkness by the ferry pilot not only had bumped the mixture control, but also the throttle, so the aircraft engine faithfully roared to full power. Fortunately the startled prospective buyer did not get hit by the spinning prop.  However, again, this was an unusual morning.  As the engine roared to life, the tiedown on the right wing broke, and the plane pivoted on the left tiedown and swung approximately 180 degrees until the prop was buried into the fuel tank of an adjacent Cessna.  Av gas was all over the place.  One thing went right that morning, in that the avgas did not ignite and there was no fireball. Unfortunately, the day was not over, yet.  After missing the spinning prop and not getting butchered by the surprise of his life, and then dodging a partially freed airplane, the buyer watched in horror as 40 gallons of avgas was sprayed over a running engine, as it came to a somewhat abrupt stop, the prop buried in someone else's wing. At that point he started running up the hill to the FBO to get help, and collapsed to the ground and died of a heart attack.
True story, and this is one that my students, private, commercial and certainly CFI, have all heard.  If it helps reinforce engine safety, and understanding shutdown and operational procedures, it is worth the time telling it.

You could use this as tangential reference: https://en.wikipedia.org/wiki/Dieseling
Engines sometimes keep running even with key off.

A remarkable story - does anyone have a source (or a debunking)?

@Joe Lee-Moyet, it happened at a local rural field. I was part owner of the plane which was hit, and had a wing replacement. I knew the potential buyer who had a nearby grass strip at his house, and owned several aircraft.  There was no NTSB report. There was a FAA investigation, and a state police investigation, both brief. Probably the only tangible "proof"   I might have is the logs for the plane which was hit, and the insurance settlement, which was multiple layers of complexity due to the many actors: the potential buyer, the airport owner, the broker, the owner, the ferry pilot, etc.

To my students the story tended to hit home because the plane which started up was also repaired, and was bought by a local. So the planes were local, and there were about 12 people who were at the airport witnessing it when it happened.

This story demonstrates a couple of threads common to a great many human-made disasters: (1) multiple redundant safety systems all had to be inoperable at the same time, and (2) bad practices that seem harmless in isolation interact in odd ways in combination. I see this sort of thing all the time in both software defect analysis and in diagnosing previous-owner "homeowner wiring" in my friend's old houses.

It's done for two reasons:

Much better for the piston rings and cylinder to not have raw fuel left in the cylinder to wash away or dilute the oil on the cylinder walls after shut down.
Carbon or lead buildup in the cylinder can retain enough heat to cook off the fuel mixture and the engine will continue to go kadunk kadunk kadunk.

Engines like the Continental A-65 used in Cubs and Champs in the 40s and 50s didn't have mixture controls or idle cutoffs (full rich all the time) and were shutoff by turning off the mags.  If a cylinder had a lot of carbon/lead deposits, it would keep running intermittently kadunk kadunk kadunk.
When you are flying floats there ARE times when you shut down with the ignition, when approaching the dock and you need the engine to stop NOW and can't wait for the idle cutoff to work.  Normally you time it with the idle cutoff so the engine has stopped before you have to climb out to step off, but sometimes you can't wait.

Unfortunately the whole 'clearing carbon / lead deposits' is an excuse many motorcyclists give around my area for needlessly reving their engines at unduly hours as well :/

Yeah I used to do it with my KZ650 although it was completely unnecessary. Old habit from the long ago days when a motorcycle engine would get fouled spark plugs after idling for any length of time.

"kadunk kadunk kadunk" see this comment

@FreeMan did you mean to link to a specific comment? Youve just linked back to this question.

@Jamiec, yeah, actually, I did. I guess I didn't do it well. Try it again

@John K, what do you mean about reason #1. Is it not true that most Otto cycle engines, on our cars, trucks, outdoor equipment, etc. shut off by removing the spark ignition? Do they have substantial life reductions for "raw fuel" in the cylinders after shutdown? I agree that as an engine cools there may be fuel condensate gathering on the cylinder interior, however, the studies I have seen, which are quite old, all show the wear effects to be quite small. Have you seen quantitative data otherwise?

Old engines with carburetors continue to pull fuel through as they wind down if the ignition is turned off.  And aircraft engines wind down quite a lot with the mass of a propeller before they stop, compared to a car engine, so there is more raw fuel than you would have with a carbureted car engine.  The proof of this is the much stronger tendency of aircraft engines to run on if shut off with ignition.  So there is significant fuel, and it is a solvent.  Solvent + oil film on a metal surface = not so good for the surface, which may sit for quite a while before used again.

Well, it is normally not "raw" fuel, it is vaporized and I agree it will condense down as it cools. But not any more than any other common gasoline engine. Are there any studies or large scale data to support your concern?  Certainly there are many engines that get frequent cycles, and are allowed to cool between them, yet we have automobile engines which last 200,000 miles which is likely more hours than airplane engines will typically see. Additionally, the airplane engine typically has much looser tolerances than an automobile engine.

Aircraft engines doen't vapourize fuel very efficiently.  In any case, if you want engineering data as proof, contact Lycoming or Continental.  I have no idea if the actual effects are enough to matter or not in the general scheme of things, and somebody would have to do an extended study on identical engines comparing the wear effects of doing it vs not doing it, which I seriously doubt has ever been done. It's one of the factors given over the years that I've been flying.

Another reason to shut down an engine with the carb in an dry state is you do not know how long it will be before the engine gets started again. A dry carb can sit idle almost forever without suffering ill effects but a wet carb will be subject to fuel spoilage/jet plugging and corrosion from water.
This isn't an issue for a carb that is run daily or even once a week.

Normally the carb is not left dry, with a mixture idle cutoff.  Rather the jet in the carb has a cam adjusting the area, and the cam moves to a position where the opening is obscured.  Of course this is not the case in many vintage aircraft where the carb is run dry by deselecting any fuel routed to it.

good point, thanks for that. motorcycle and lawnmower carbs also lack that feature and need to be shut down dry, or their fuel must be doctored with preservative during periods of nonuse.

The stale fuel fouling the carb issue has become more of an issue in recent years, well after the institution of mixture/idle-cutoff aircraft engine controls. Actually I think it related to the use of ethyl alcohol.

This is a basic question that should be covered by your ground school, flight instructor and your primary training.
The vast majority of certified piston-engine airplanes have two (redundant) magnetos for ignition.
The mag switch in OFF position grounds the magnetos so they don't produce a spark even when they are turning (like if you pull the prop through a 180 degrees.)
The ground wires are called P-Leads. If the ignition switch or one or both P-lead should fail (open the ground circuit) the magneto(s) may be "hot", that is, they can produce a spark in the spark plug and ignite any fuel in the cylinders. This will kick the prop over with great force and possibly hit anyone/anything in the prop arc.
By pulling the mixture to cutoff position, starving fuel from the engine to shut it down, you greatly reduce the risk of a surprise/unwanted engine start when the prop is next moved.
You might just move the prop level to allow attaching your tow bar after flying, or someone may handle the prop for no reason at all (curious children or just idiots at the airport/airshow/fly-in) and if the engine makes a spark and fuel is available (shut-off carb "rich") there could be an injury, death, and resulting lawsuit.
Teach your flying guests, especially children, to never touch the prop unless they are certain it is safe. The key may be left on, or the mixture rich, and accidental starting can occur.
Your handy pilot's checklist should have "Mixture - idle cutoff" in the "Before Starting"  and "Shutdown"  sections.
Lastly, never leave a nosewheel towbar connected when you are not moving the airplane. It is very easy to forget it before starting the engine, and ANY PROP STRIKE REQUIRES A PROP INSPECTION AND ENGINE TEARDOWN/INSPECTION. Add "Towbar Stowed" to your preflight checklist.


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Where to find historical locations of North Atlantic Tracks?
I'm looking for historical, daily locations of the North Atlantic Track (NAT, published daily as NOTAM) system for the past 10/20 years.  I've already contacted what feels like dozens of organizations (FAA, Gander, Shanwick, ...) but no-one seems to actually archive the NAT locations.
I'd be extremely grateful for any pointers towards possibilities to acquire these data, be it free or paying.

Did you check this site http://notams.aim.faa.gov/notamSearch/

@D_S thanks for the pointer; however, I cannot seem to be able to find NAT advisories using their search form ...

This guy has a 365 day history online.
You could contact him for older values.
You can also get some history using Archive.org.

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Is a single-engine ferry flight allowed with a twin-engine plane?
If a twin-engine aircraft has an engine problem and could fly somewhere for maintenance, is a single-engine ferry flight ever allowed? If so, do airlines or pilots ever decide to do this?

I can find no evidence of the FAA or any other authority ever issuing such a permit.
It has happened, though (without a permit). An SN-601 tried to take off from Portland with one engine. Unsuccessfully. Luckily no one was hurt.
There's also a lengthy thread about it on airliners.net, in which there are several undocumented, anecdotal stories about this being done successfully (and illegally), e.g. in a P-38 and either a Convair 240 or 600.
There are some good technical reasons why this is unlikely to be safe, or approved by any authority:

Asymmetric thrust will make the takeoff very difficult. In particular, until the airplane reaches VMC, it may not be possible to keep the airplane on the centerline with takeoff thrust on one engine.
Especially for piston airplanes, single-engine performance is often very poor. Hence the expression, "in the event of an engine failure, the other engine will get you to the scene of the crash."
All-engines-out operation in a multi-engine airliner is usually considered an extremely unlikely event, and as such, training is patchy and contingency procedures are very dire if they exist at all. Basically, if your one good engine dies, you'd be in mortal danger, much moreso than in a single-engine airplane, in which pilots are well trained for engine failures, since all-engines-out is a much more likely event.

Back to the notion of ferry permits, some guidance is given in 14 CFR §91.611, which lays out conditions for one-engine-inoperative ferry permits for 4-engine or 3-engine-turbine airplanes. It says nothing about twins though.

I know that in the three engine Falcon's that there is an AFM procedure for a ONE-engine-inoperative ferry.  Never seen that in a two engine airplane though.

Normally on approach one is trained to keep thinking "go around", except when single-engined.  A single-engine go around is so risky that you're trained to commit to the landing and just don't mess it up.  :-)  A single-engine takeoff would be much worse.  I've done single-engine go arounds in a lightly loaded Twin Comanche.  It's doable, but in the same configuration we could also slightly climb at 6000 feet single engined.  For those twins that can't climb single above 2-3000ish, that would not have gone well...

@BrianKnoblauch - single-engine go-arounds are quite doable and less dangerous (though they still carry a greater degree of risk) for jets, but this is owing to their much greater thrust. Even light twins aren't quite as doomed, but should a go-around be attempted, there needs to be sufficient altitude to clean up the aircraft prior to initiating the climb. Many light twins simply cannot maintain altitude in landing config, but will usually be more than capable of climbing back to pattern altitude otherwise... at least at low-altitude airports.

Civilian aircraft are not designed for this - but some military aircraft are. The Antonov-70 can easily take off with one engine inoperational (it has four in total), but it has a limited capability to take off with two engines out on the same side! For that, it has to be empty and can carry only minimum fuel.

This capability is the consequence of the demand of the Soviet Air Force for the An-70 to operate for 6 months with minimum maintenance. The Antonov design bureau, well aware of the limited capabilities of front-line troops in aircraft maintenance, designed this transporter with lots of redundancy.

Edit:
With one engine inoperational, any twin-engined civilian aircraft would not be legal if it attempted a one-engine take-off. I would expect there is a way to do it, but it needs the agreement of the owner and some paperwork with the local authorities. If you can prove that this particular ferry flight is safe, I think you would be allowed to fly. But I am certain that without lengthy preparation and paperwork there is no way to legally take off on one engine only.
This is in contrast to military aviation where this kind of operation is planned for.

Large aircraft with huge power reserves probably could, assuming you can find a pilot willing to do it. A twin-engine fighter like an F-18 very likely can - the single-engine thrust-to-weight ratio is nearly double that of a 777, and if you light the afterburner it has more thrust on one engine than a 777 with both mills turning.
Smaller piston twins usually cannot - one engine is not enough.
The crash rate for light piston twins is (or used to be) much higher than that of piston singles. The reason: the asymmetric thrust made them much harder to control to the point where the occasional instructor said "if one engine goes, feather the other one too".
One notable example is the Cessna Skymaster - two engines, centerline thrust. notable enough that the FAA created a multi-engine license category just for it. Common accident mode in the Skymaster is feathering the wrong engine in-flight, and the number of takeoff failures with the back engine not running says it won't take off on just one either. Maybe if you removed the prop, no passengers, minimum fuel and a really long runway. Check your life insurance first.

"and if you light the afterburner it has more thrust on one engine than a 777 with both mills turning." You mean higher thrust/weight ratio, right? There's no way an F414 can even get close to the output power of a single GE90, let alone 2 of them. 22,000 lb of thrust falls a bit short of 115,200 lb (let alone 230,000 lb.) - lol

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If I own land, can I create a private runway on my property for my own use?
In the United States, if I own land that has an area suitable for landing a small general aviation airplane, can I just create a private runway, or do I have to officially be registered with the FAA or some government agency?

In short: Yes, you can. The FAA doesn't really care, as long as you're not going to interrupt class B or C operations. And honestly as long as you're not hosting a dozen other aircraft, how are they going to tell the difference between a field and an airstrip? If you want it on a chart or you are near special airspace, you need to contact the FSDO and talk to them about it (it's good to do that anyway). They will send someone out to survey it and talk with you, and hopefully approve it.
It's the local authorities that usually ends up being troublesome. Your state/county/city might have laws that apply, and you'll need to find that out on your own. A friend of mine spent just a few days talking/meeting with the FAA on his strip, but spent weeks dealing with the state transportation department and a local ban on new grass strips which he sat right on the border of (as in it was a ban in a 50 mile radius and his house was on mile 50).
Persistence is key, good luck!

I guess neighbors should be consulted too, otherwise they can construct something at the ends of runway (if it borders their land) and obstruct the runway.

@Farhan great point. Coincidentally, the friend from my story did his rounds letting neighbors know what he was planning, and found out that one of them was an airline pilot who volunteered to help with construction.
In my case, I just got a few "A what?" and a few sighs.

@Farhan The neighbours should definitely be appraised and preferably, on board, however, once you do have all the local permits, you should officially register your airstrip with the FAA, as it then prevents neighbours (or the government) from building anything that will be obstruction in the flight path.

@Farhan If you jump through the hoops to register with the FAA as a private airport, you gain legal protections against construction of new obstacles by your neighbors. You’re stuck with any existing ones, though.

I have read of another who went to the trouble of registering their strip - worked out well when a power company wanted to run high voltage lines right over the middle of the strip. Since it was a registered airport, they had to run the lines elsewhere.  Here it is, the 2nd answer:  Why do farmers register their fields as airports?

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In a 747 is it normal for the Vr (takeoff speed) to vary greatly depending on fuel load and ambient temperature?
I was reading one of the documents linked on this question, particularly I was reading case study number 8 of this particular document.
In the conclusion the author notes that the aircraft flight characteristic calculations had been messed up to the point that all V-speeds were calculated for a 747 100 tons lighter than their actual Take Off Weight (TOW).  Thus, they tried to rotate too early, couldn't get enough lift and the tail of the 747 struck the ground.
When reading that brief description, I had assumed that perhaps they were off by 5 to 8 knots, or something along those lines.  So, I was surprised to see the author later note that Vr was actually off by close to 30 knots!
I'm really curious suddenly, how much can a 747's rotation speed change?  I was told that rotation speed was generally somewhere around 130 knots for that class of plane, but if there is a 30 knot variance. Can it really be anywhere from 115 to 145 depending on the weight of the plane?

As Henning Makholm's answer discusses, the weight difference between the lowest and highest weights is significant. The operating empty weight (OEW) of a 747-400 is 394,100 lb, while the maximum takeoff weight (MTOW) is 875,000 lb. This means there is a difference of about 400,000 lb between the lightest and heaviest weights at which a 747 may be taking off, making the MTOW about twice as heavy as the OEW.
The rotation speed Vr is the point at which the aircraft can pitch up and develop enough lift to climb. So at MTOW, the 747 must develop about twice as much lift than closer to OEW. Most of this force is lift from the wings.
Lift can be calculated with the following equation:
L = 1/2ρv2sCL
L = lift
ρ = air density
v = airspeed
s = wing area
CL = lift coefficient
The air density will certainly play a role. Higher altitudes and temperatures reduce the amount of lift. But this example pertains to the other variables.
An airliner can use flaps and slats to increase the CL and s of its wings.
The CL will also depend on the angle of attack α of the wings. An approximate curve for the 747 can be seen here (it's for a 747-200, but it should be close enough). When an aircraft rotates, it is changing the AOA, which increases the lift. It is very important when designing an aircraft to make sure it can pitch up enough while on the runway to achieve the pitch angle needed for takeoff. A 747-400 rotates to about 10 degrees on takeoff. Based on the approximate CL-α diagram, the lift coefficient changes from about 0.3 to 1.25 when α changes from 0 to 10 on rotation.
When the aircraft weight is increased, flaps may be increased from 10 to 20. However, flaps 20 may be standard because these guys said so, so lets assume that CL and s will also not change. This leaves the airspeed v as the only parameter left to increase lift.
In this study, figure A-7 shows a distribution of ground speed at liftoff that lies between 140 and 190 kts. These numbers will probably be a little higher than Vr due to the acceleration between Vr and liftoff, and an average headwind. This means that at weights at the lowest end, 130 kts would be a reasonable estimate for Vr.
So now lets make up some numbers. Lets take the weights 475,000 lb and 875,000 lb. Assume that the aircraft needs a lift 10% higher than its weight to take off. This gives us lift values of 522,500 lb and 962,500 lb. Using the lift equation and a low end speed of 130 kts to find the unknown portion.
522500 = 1/2ρ1302sCL
ρsCL = 61.8
Since we are assuming none of those vales will change, we can solve for v at the higher lift value.
962500 = 61.8/2v2
v = 176 kts
This is not too much lower than the high end liftoff value of 190 kts. So there you have it. Lift must be increased to account for the additional weight, and lift is proportional to the square of the airspeed.

Man, I wish Terry would show up and tell us some actual numbers to throw into the formulas.  I'm a little dubious about my 115kt take off speed for OEW...

@JayCarr I agree. In the meantime I added some statistical values to go off of.

Below are the lowest and highest Vr listed for 747-100 and -200 aircraft with the engines shown for a flaps 10 normal takeoff. They are from the Tower Air (now long defunct) QRH that pilots and engineers were issued.
JT9D-3A  110 to 174
JT9D-7A  114 to 177
JT9D-7F  115 to 179
JT9D-7J  118 to 180
JT9D-7Q  126 TO 182

The actual tables are lengthy, with the Vr varying according to takeoff weight, flap setting, temperature, pressure altitude, as well as at least one other thing I cannot offhand remember. Each cell of the table gives V1, Vr, V2, and the 3-engine rotation target. Lowest weight, of course, gives you the lowest Vr.
The f.e. grease-penciled the values he looked up on a plastic card, which he then passed to the f.o., who checked them. When the f.o. was satisfied they were correct, he propped the card against the instrument panel in front of the thrust levers. The captain could choose to accept them at face value or check them himself as well.
At the two 747 carriers I worked, there was a difference in culture as to how you were to rotate. At the first carrier, you rotated to 10 degrees nose up and held that attitude until you came off the ground, at which time you rotated to the 3-engine rotation target. This procedure was intended to prevent tail strikes. At Tower Air they taught the correct procedure (in my opinion) of rotating directly to the 3-engine rotation target.

Why, in your opinion, is the latter method of rotating the correct one, if the former method comes with a reduced risk of a tailstrike?

@Sean From memory and almost 30 years ago now, EIA my first 747 carrier, had stretch DC-8s, which apparently were prone to tail strikes (see https://www.quora.com/How-common-are-tail-strikes-during-the-normal-operation-of-passenger-jets). When they got 747s, their first captains were former DC-8 captains and they brought with them that culture. Boeing's procedure was to rotate directly to the rotation target, knowing that before you get there you will be off the ground. I was criticized and laughed at in the sim during my initial training for Tower Air, for the 10 degree procedure.

@Sean I forgot one thing (and I was out of room in my previous comment). If you rotate to 10 degrees and then wait for the aircraft to lift off, your ground run will be greater than if you rotate directly to the 12 to 14 degree (usually) target. Also, when EIA got their 747s, they didn't hire any experienced 747 captains to the best of my knowledge. Tower Air, on the other hand, had only 747s and hired experienced 747 captains right off the bat as a startup.

So, if you try to rotate directly to the target pitch attitude in a DC-8-60/70, you'll get a tailstrike, whereas a 747 will lift off before a tailstrike unless it's very severely overloaded?

@Sean I think abetter statement would be that for max weight takeoffs, unless you rotate to the target attitude slowly, you're liable to get a tail strike. Tail strikes on 747s were just not a problem, even when overloaded. See talking-of-flying.com#overloaded. There was no tailstrike.The 747 sits higher and it has a body gear well aft of the wing gear. The angle from the aftmost gear to the tail is greater on the 747. Tailstands were typically used when loading stretch DC-8 freighters, but not typically used for 747 freighters. Also, 747 target rotation attitude can go as high as 18 degrees.

It doesn't sound surprising to me.
There's more than a factor of 2 in difference between the empty weight and the MTOW of a 747-400, so one departing close to empty will be able to produce lift enough to climb away from the runway at a significantly lower speed than a fully-loaded one -- and therefore it should, because (all other things being equal) the quicker you get to altitude, the shorter a window is there for sudden problems to be immediately dangerous.
Since lift increases with the square of the airspeed, one would expect vr for an almost empty 747 to be less than 70% of that for the same aircraft at MTOW under similar conditions.


text:
Why did this pilot have his single-engine license revoked?
5 minutes into this video, a commercial Indonesian pilot is shown performing a very tame version of a parabolic flight path as performed by zero-gravity flights, in a Cessna 172.
This video has over 11 million views currently and due to the 'wrong' people presumably having seen this footage, the pilot has had his single-engine license revoked. There is currently a petition to have his license re-instated and the coverage in Indonesia is widespread.
What actual laws or regulations did he break? Seems like he performed the maneuveur safely to me.
Link to news story (translated to English)

Not many light aircraft pilots haven't done the floating pencil trick. Which is basically this. In any case, what evidence do we have that the pilot has "had his license revoked"? Can you link to where you learned this info?

@Jamiec Sure... all you had to do was search 'Indonesia zero gravity' in Google news. You'll need to translate the page obviously: https://www.cnnindonesia.com/nasional/20190529155704-20-399507/aksi-zero-gravity-kapten-vincent-raditya-berujung-kontroversi

Right, and if you had done exactly that then it quotes the Director General of Air Transportation explaining exactly what the pilot did wrong. So, what is your question exactly?

@Jamiec So the answer is, you need to be a flight instructor to perform this manoeuvre? That's what the article states, yes, but I cannot find sources that confirm that anywhere. Hence the question.

@Cloud He broke his country's regulations. Period. Regulations are not black and white for a good reason. "Reckless" can be objective and subjective. Only thing he can do is appeal, but I doubt he will appeal.

Another minor point: You can perform a manoeuvre safely and it still be against a regulation. I could safely fly inverted past Heathrow's tower. Doubt i'll keep my license though.

Lets break this down as best we can.
For starters you've made an error in your assertion. The pilot hasn't had their license revoked, just simply their SEP rating. There's a difference. The person in question can still do their day job as a pilot, on a type-rated aircraft. They have accepted a suspension of their Single Engine rating.
On some finer points mentioned in the linked news article:

[...] both pilots and passengers do not use shoulder harnesses

The Indonesian Aviation Regulations specify

For small civil airplanes manufactured after [27 December 1993], an
  approved shoulder harness for each front seat.

If we make an assumption that this flight was carried out in an aircraft manufactured after 27th December 1993, then both front seats should have been equipped with shoulder harnesses which should have been worn. Hardly the crime of the century, but there you go.

Second, Vincent gives flying control to unauthorized people

This one is a bit tenuous, unless the PiC has an instructor rating he is "officially" not supposed to allow someone else to manipulate the controls. Finding exact wording to back this up is not easy. I think most pilots (of light aircraft) have let their passengers have a go at the controls.

Third, he was deliberately maneuvering zero gravity

This in and of itself isn't the problem, I suspect the problem was whether he was doing so in an entirely safe manner. He gave no warning to his passengers that I could see, and I'm not convinced he performed the checks suggested before such a manoeuvre that would make it safe.
They could easily just cite the following:

No person shall operate an aircraft for the purpose of air navigation or for operations on
  any part of an airport (including areas used by those aircraft for receiving or discharging
  persons or cargo), in a reckless or reckless manner so as to endanger or be likely to
  endanger the life or property of any person.

The wording of this regulation is fairly similar across many aviation regulators, and is often cited for "You did something against regulations".
Sources:

CIVIL AVIATION SAFETY REGULATION - Republic of Indonesia

It's not clear to me if this answer is using the phrase "checks required before such a maneuver" to indicate a specific regulatory requirement to do a HASELL check before exceeding a certain pitch or bank angle, or is just referring to the catch-all regulation cited immediately after.  It appears to be the latter and if so do we really know that the maneuver was unsafe because the pilot didn't perform a HASELL check?

@quietflyer we don't know anything it's all purely speculation. Unless the Indonesians release a report on this incident we never will. I clarified the other point you made.

"gives flying control to unauthorized people": is that actually visible in this video? I didn't see it.

The main thing was the pilot posted a video for all to see which would be almost like a challenge to the authorities to do something to discourage others.

I expect zero G to be outside operating limit of aircraft.

@GiacomoCatenazzi: I do not, but pulling out of the ensuing dive might exceed the G limits.

@Joshua: In my understanding zero G is not about reaching structural limits, but about hydraulics and fluids.Fuel should enter to the engine (possibly without bobbles of air). It is not complex to adapt (by keeping pressure, etc.), but I'm not sure it is regularly done,

@Giacomo: An airframe usually has a positive and a negative gee rating.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
What should I expect to happen when I get on a skydiving flight
I am schedule to go on a short flight (skydive)* on a Cessna 208B Grand Caravan during an international visit to some friends. I found the serial number of the flight, here is it's record.
Since privately owned aircraft within skydiving community are known not to be maintained as well as commercial operations and sometimes these pilots have very little flying hours, is there anything I as a passenger can do to improve the safety of the flight? For example, what pre-flight checks should the pilot make before taking-off?
Note* Related to this question.

is there anything I as a passenger can do to improve the safety of the flight

You should do exactly what your told, when your told and make sure you keep well clear of spinning propellers. You will have a marshall or the pilot themselves guiding you when airside - do exactly as you're told!

what pre-flight checks should the pilot make before taking-off

If it's the first flight of the day the pilot will do a walk around of the aircraft. They will check the general airframe, as well as some specific things

The static ports being clear
Pitot covers/control locks all removed (those little red dangly things that say "remove before flight")
Control surfaces have free movement and their connecting rods are secure
Tyres & brakes satisfactory
Fuel is sufficient and uncontaminated
Propeller(s) undamaged
Oil sufficient in engines
... and a load of other things!

Before each take-off the pilot will also run the engine up and run it at idle. Just before take off they will perform some pre-takeoff vital actions. You will probably not notice any of this, but I assure you they'll be doing them - they may take mere seconds.

One thing to look (not just for this, but for with all aspects of aviation) is evidence of a Safety Culture. A skydiving operation is no different.
Skybrary defines Safety Culture as follows:

Safety Culture is the way safety is perceived, valued and prioritised in an organisation. It reflects the real commitment to safety at all levels in the organisation.

It should be clear to you as you interact with the company what their commitment to safety is. Do they have materials on the walls of their place of business with safety reminders? When you talk to them, do they appear to take safety seriously or does it seem to be an afterthought? Do they take time to address your concerns or do they brush them off?
It really comes down to professionalism. Do they wear uniforms, keep schedules, offer clear communication? It's not that these things make it safer, but safe operators tend to do these things.
If there is a unified message of safety that is repeated by everyone you contact, from the person checking you in, to the parachute rigger to the pilot, it's likely that they have a strong safety culture.

Safety Culture can have a direct impact on safe performance. If someone believes that safety is not really important, even temporarily, then workarounds, cutting corners, or making unsafe decisions or judgements will be the result, especially when there is a small perceived risk rather than an obvious danger.

You ask about preflight checks that you ensure a pilot does prior to take-off. In an environment like a skydiving operation, you might not see things like the pilot using a checklist because the pilot typically flies the same flight over and over again, many times in the same day, and likely uses a "flow" and doesn't verbalize the checks they are doing. They will likely look "relaxed" to you because they are doing this multiple times per day, but you can see, do they do things without rushing, make smooth adjustments? Again, it's not that this makes it safer, but safe operators tend to do these things.
At the end of the day though, like the other answer says, you have two options: trust the pilot and aircraft are competent and able to take the flight, or don't take the flight.
Occasionally when people look at me like I'm crazy for flying, I say "well I don't want to die, either, so I'm going to do everything in my power to minimize the risk of that happening on this flight." I'm sure the pilots of jump planes feel the same way.

There's only one guy on board with a 'chute. I know who I'd trust :)

haha, exactly! Now if you climb in and you see a chute on the pilot...

That last paragraph pretty much sums it up for me.

https://www.jetphotos.com/photo/7629415  The pilot does have his own door for getting out. FAA regulations require wearing of chutes if more than 60 degree bank angle or 30 degree pitch angle is used - so the pilot may be wearing a chute if dives are used to get back on the ground quick for the next load of jumpers.

Increasing your safety is easy:

Focus on your jump
Remember what you have been instructed
Don't interfere with other people jobs

Doing otherwise would be counterproductive, distracting you and the other people doing there jobs, increasing chances that someone would make a mistake.

Since privately owned aircraft within skydiving community are known not to be maintained as well as commercial operations

They are? According to whom?
And it's wrong anyway, skydiving clubs are commercial aviation operations.


text:
What part-time opportunities are available for low hours pilots?
I hold an NPPL and have a career that I very much love and wouldn't want to change. However, I would also like to make some money from flying.
What, if any, part time opportunities are available for someone with under 200 hours? Would anyone hire such a pilot for crop dusting, private transport, cargo or other jobs and only need someone recreationally?
I understand this might be far fetched and would also potentially involve upgrading to a PPL and getting instrument and/or commercial ratings added too.
Additional sub-question. If there are opportunities available, how does one find them?

Possible duplicate https://aviation.stackexchange.com/questions/65917/what-steps-do-i-need-to-follow-to-use-my-ppl-for-income

Is the UK NPPL similar to the US sport pilot certificate or recreational pilot certificate?

With an NPPL, you have no option to earn money from flying.
Upgrading to a PPL would allow you very limited opportunity to earn money.
The first step is possibly a Class Rating Instructor which allows you to do things like club checkouts, revalidations etc.
Beyond that you could go for a fully fledged Flight instructor rating which would allow you to teach up to the NPPL but not the full PPL.
To teach PPL, you need the FI rating and at least the CPL exams, but almost everyone will advise you to go full CPL as the difference between CPL exams only and full CPL is just a few hours instruction and some flight time.
The best place to ask about such opportunities would be your local (or not so local) flight school. Check out the schools at your local airfield.
You can also tow gliders with a PPL, it wont pay you cash money, but it will pay you in flight hours. Its almost exclusively done by pilots with glider experience, so if you want to do that get going with your local gliding club.
Almost every other paying flying position will need a CPL at least.

Maybe worth noting that this isn't a "nobody will hire you" thing. Even if somebody would, e.g. pay you to fly some package over to their friend, you're legally barred from "commercial operations" without a CPL.

To add the above comment, I obtained a CPL-H in early 2001. The road to employment is long and difficult even as a CPL holder. It's possible if you are willing to relocate large distances, and probably remain unattached (so that you can relocate as needed, when needed). My perspective is from Canada. I never made use of my licence.


text:
Why does the KC-46 use an MCAS?
The KC-46 tanker aircraft (the U.S. military's designation for the 767s it uses as tankers, and which every other country calls the KC-767) uses an early version of an MCAS.1  This was ostensibly developed to cope with shifts in the aircraft's weight and center of mass during aerial-refuelling operations:

...  The KC-46 uses a similar system because the weight and balance of the tanker shifts as it redistributes and offloads fuel. The KC-46 has a two-sensor MCAS system, which “compares the two readings,” the Air Force said.

However, even though changes in weight and balance as a result of onloading, transferring, and offloading fuel are common to all tankers, and, yet, the KC-135, KC-10, KC-130, KC-30, et al, do just fine without any MCASesque system.
What makes the KC-46 special in this regard?

1: The KC-46's early-model MCAS was later developed (incompetently) into the MCAS version used on the 737 MAX.

Just spitballing here - maybe because it is the newest of the tankers, and computer processing power had improved enough to easily implement the controllers needed for improved flight control characteristics?

The real question is, if they had a previous system that compared two sensors, why would they only use one sensor on the 737MAX?

One only speculate that it was a cost saving measures. One less probe, less installation cost.


text:
Did Concorde really fly above 55k feet as mentioned in this report?
Here is a report of the last journey of Concorde from JFK-LHR, which mentions "The highest altitude we reached was 58000 feet." Is this height aerodynamically feasible to reach?

Sure, why not? You should check out the U-2 or SR-71 ceiling.

@DavidRicherby I mainly wanted an answer to "Is this height aerodynamically feasible to reach?", which can't be googled. I have been  here for more than a month now, and do care to not ask those silly questions!

@anshabhi You're asking if the height is feasible to be reached by a specific plane. Googling "concorde maximum height" immediately tells you "Concorde had a maximum cruise altitude of 18,300 metres (60,039 ft)" without you even needing to follow a link. Comparing that answer with the value you're asking about (58,000ft) immediately tells you that it is aerodynamically feasible to reach such an altitude.

See also http://aviation.stackexchange.com/a/17667/1289

That answer is a "Peter Kämpf
", the mark of excellence! And ya, if I could I would have marked that as accepted.

Yes. The extra height was necessary in order to reach lower pressure air, and thereby reduce drag, and heating of the airframe from supersonic compression of the air.
Concorde's windows were extra small, so that if a window did blow out, the air compression system could actively compensate by pumping air in faster than it could escape, until the pilot completed his emergency descent.
More details can be heard on this podcast.

That was a great episode! Definitely recommended for any Concorde (or even aviation) fan.

The density will go down a bit at that altitude compared to normal aircraft, but your airspeed is Mach 2, so that's good. Lift is (among others) a factor of both parameters. Be aware that there is a bit more going on though with supersonic stuff as well.
An increasing number of aircraft are approaching this altitude domain. For instance, the subsonic corporate Gulfstream G650 tops at 51,000ft.

Why do you avoid the term "dynamic pressure"? Adding this should improve the precision of your answer.

Yes. According to Wikipedia, Concorde's service ceiling was 60,000ft.

As per its service celling that would not have been an issue. It should also be noted that Mach 1 (the speed of sound) is about 90 Knots Slower at that altitude.

So when Concorde was said to go Mach 2, is that at the altitude it was flying at or at sea level?

Mach 2 is relative to the exterior pressure. I think it could only reach those speeds at higher altitudes for pressure reduction needs. However at that altitude Mach 2 would be slower (ground speed) than at sea level. FWIW the Mach Number is not actually speed so to speak. Its a dimensionless number that depends on local factors. https://en.wikipedia.org/wiki/Mach_number

"Mach 2 is relative to the exterior pressure" -- strictly speaking, relative to the exterior temperature, I think. https://en.wikipedia.org/wiki/Speed_of_sound#Altitude_variation_and_implications_for_atmospheric_acoustics


text:
How do non-US pilots get the hours necessary for an ATP?
I'm wondering about the possible lack of real-world flying experience by pilots in non-US carriers
In the US, aspiring airline pilots can work at a variety of jobs, like instructing, towing banners, crop dusting, etc, or part 135, to build time towards the 1250 hours now necessary for a restricted ATP to act as Second In Command (SIC) in carrier operations.
How do non-US pilots who don't have a military aviation background build the hours necessary to obtain an air carrier license in their own country? Are they all ex-military? Do they only need an ICAO-compliant commercial license and not an Air Transport Pilot License (ATPL)? Do we have 250- or 500-hour commercial pilots flying SIC into JFK?  Do these pilots have experience flying non-pushbutton aircraft?
Not sure if this is credible, but, as an example, there are fewer than 30 non-air carrier turboprops (Caravans, twin Cessnas, twin Beeches, and a lone Cheyenne) registered in Malaysia, and 10 are registered to the air force. The same site says Jordan has 7, 6 of them in the air force. Where are the national air carrier pilots getting their twin time? SIC in domestic carrier ATRs and Dash-8s?

probably an equivalence certificate from the agency of their home country

@CGCampbell i clarified the question

Are those jobs to build hours not available in other countries?

Because crop dusting, banner towing, instructing are unique to the U.S.? And that isn't even close to an exhaustive list of potential employment.

Some countries don't have many (any?) of those jobs, no -- airline cadetships are much more common in other parts of the world.

Please bear in mind that not everyone lives in the USA. "Foreign" doesn't mean "outside the USA" to all of us. Indeed, the US is foreign to 95% of people on the planet (though presumably not to 95% of readers here).

Feel free to edit to make it less Us-centric

Under the rules of ICAO Annex 1, Personnel Licensing, you don't need an ATP License to fly as second in command (SIC) on a commercial aircraft required to be operated with a co-pilot. A commercial pilot license (CPL) is sufficient to be SIC on an aircraft that requires to be operated by more than a single pilot.
And since 2006 ICAO have defined a Multi Crew Pilot License that also allows a pilot to be second in command on a commercial air transportation multi-crew aeroplane.
The  ICAO website about Multi-Crew Pilot Licence (MPL):

The MPL allows a pilot to exercise the privileges of a co-pilot in a
  commercial air transportation on multi-crew aeroplanes. It provides
  the aviation community with an opportunity to train pilots directly
  for co-pilot duties. It is a new licence that has been introduced in
  addition to the existing pilot licences defined in Annex 1 — Personnel
  Licensing.
The licence focuses on ab initio airline pilot training.
  MPL training and assessment will be competency-based and involve a
  multi-crew environment and threat and error management from the onset.
  It provides for greater use of flight simulation training devices and
  include mandatory upset training. At this stage, only aeroplanes are
  considered for this new licence. The details of the requirements for
  the licence are contained in Annex 1 — Personnel Licensing and in the
  Procedures for Air Navigation Services — Training (PANS-TRG). These
  documents outline the minimum international Standard for the
  implementation of the MPL by any State; they can be purchased directly
  from ICAO through the Document Sales Unit.

In Annex 1, the requirements are laid down for the MPL. One of the requirements says:

Experience
2.5.3.1 The applicant shall have completed in an approved training course not less than 240 hours as pilot flying and pilot
  not flying of actual and simulated flight.

The MPL, combined with a type rating, will get you to the right hand seat of the aircraft of choice.
So it's likely there are 250-to-500-hours commercial pilots flying Second In Command (SIC) into JFK. With experience in Beech Bonanza's, Cheyenne/Seminole, maybe CitationJet, a lot of simulator time and a couple of hours in a B777.
To answer your title question, in many countries pilots get their ATPL after building hours as SIC flying with a CPL or MPL within an airline training scheme.

Would a 250 or 500-hour pilot be able to get an ETOPS rating? At any rate, those requirements seem concerningly low. You can't fly a crop duster or a banner with 240 hours in the U.S., let alone an airliner. Also, would the FAA allow such a pilot to fly into U.S. airspace in an airliner? Don't you have to get your license endorsed by any countries in which you're flying? How does that work where no such license exists, as in the case of the U.S.?

@reirab that would make a good follow up question.

Wouldn't newly minted MPLs be more likely to go into line domestic flying than international due to seniority, anyway? Or are there airlines where this doesn't hold?

@UnrecognizedFallingObject Domestic in countries with fewer airports than fingers on one hand..?

@DeltaLima I agree that it would make a good separate question. I'll probably go ahead and post it as such. The reason I mentioned it here rather than doing so initially, though, is that its answer is necessary in answering the Do we have 250- or 500-hour commercial pilots flying SIC into JFK? part of this question (well, unless the answer to that were already 'no' for another reason, in which case it would be moot.)

@DeltaLima -- I suspect very few of those flag microcarriers are set up for ab initio pilot training -- AIUI, most ab initio ATPL training is performed by larger, established airlines such as LH, Swiss, or Qantas.

@UnrecognizedFallingObject Countries without a domestic market don't necessarily have flag microcarriers. Swiss, from your example, has only two domestic routes. KLM, not exactly a microcarrier either, has none.

well, in Brasil, the market used to be divided into int'l and domestic carriers. Varig was the int'l carrier, but TAM and VASP were two of the domestic carriers. VASP (where I worked, but not as a pilot) had one international R/T each week, a charter to Orlando.

@DeltaLima -- I stand corrected then.  I wonder how seniority impacts route selection for say KLM, then?

@UnrecognizedFallingObject There are of course popular  and less popular destinations that a fleet serves, depending on the city, flight times, hotel etc. The higher your seniority the more likely it is you will get to fly your preferred destination on your preferred date. And in general, senior captains with grown up children have different preferences than First Officers with young children or CoCo-pilots (yes, KLM has them) without a family to take care of. BTW, KLM does not fly with MPLs, only CPLs and ATPLs.

Well it's much harder to get inside a cockpit without such opportunities. In Europe, we have some carriers (for example Lufthansa or SWISS) who offer ab initio programs. You can also make an ATPL at a flight school but chances to get a job afterwards are almost zero. Some carriers have job offers for "Ready Entries" with frozen ATPLs and without Type Rating but that's a minority.
In most cases to become a pilot you need to get one of the rare ab initio places.
All in all I thing it's harder to become a pilot in the EU than in the US.


text:
How come sonic booms only occur once at the speed of sound and not multiple times?
Fighter aircraft today are capable of flying several times the speed of sound. Why is it that the sonic boom only occurs at the moment the plane crosses Mach 1?

Sonic booms are a continual process once your are at and above Mach 1.  You only experience it as a single boom as the shockwave passes you.

Are you suggesting that a sonic boom only happens as an aircraft crosses Mach 1, and then vanishes as it continues to accelerate? That is not the case.

I will admit also I thought along the same lines when I was younger... I never quite got the idea until a few years later.

@DavidRicherby I was unsure if it was a question of (a) why it only occurs above Mach 1 (which IMHO the marked duplicate answers) (b) why it does not occur multiple times (i.e. multiple sonic booms for every Mach, indeed a new question) or (c) if it only occurs as a one-time event (which is wrong and would indeed be a new question). The question and text is somewhat ambiguous. Perhaps the author could elaborate a little and I would be happy to reopen it. As it stands I am unclear exactly what he would like to know...

@MikeFoxtrot Taking the title into account, I'd say the question is "Why does the sonic boom only occur once? By the way, the one time it occurs is the moment at which the aircraft passes Mach 1."

@DavidRicherby Fair enough; In that case I would reformat this one clearly with that interpretation since that's a decent question. If we're wrong he could still open a new one later. Update: Changed the question correspondingly.

Sonic boom is well explained in What is the simplest way to explain a sonic boom that is still technically correct?, including when it happens (particularly this answer).

Your question is:

Why is it that the sonic boom only occurs at the moment the plane crosses Mach 1?

The answer is: It doesn't. Sonic boom first occurs when the plane crosses Mach 1 and the plane continues producing sonic boom as long as the speed stays above Mach 1.
Another part of your question is:

How come sonic booms only occur once?

And the answer is: because the plane flew over you once. If the plane were to turn around and fly over you a second time you'd hear two sonic booms.
When you hear a sonic boom it doesn't mean that that boom was generated at Mach 1. It only means that the boom was generated at speeds equal to or greater than Mach 1. For example, a plane travelling at Mach 3 would still produce a sonic boom but you'd still only hear it once because the "boom" would only reach your ear once.
To understand this you need to understand what a sonic boom is.
Various parts of the airplane generate sound. Form the roar of the jet engines to the whistle of the skin of the aircraft moving through the air.
When travelling at normal subsonic speed. These sounds travel normally through the air and what you hear is a continuous sound of an airplane flying.
When travelling at or faster than the speed of sound, all these sounds arrive at your ear simultaneously. That is to say, if normally you'd be able to hear a plane passing overhead over a period of 10 seconds (for example) then at supersonic speeds all those 10 seconds of sounds (engine roar, woosh of the wings etc.) arrive at your ear at the same moment.
Since all the sounds you'd ever hear from the airplane arrive at the same time, the result is a very loud boom (all the 10 seconds or more of sound added together).
That's why you only hear it once typically.
There are exceptions though. If the plane is long enough, and the nose and tail generate loud sounds, it is possible to experience a double sonic boom caused by the tail generating a second boom. But generally, even a very long plane like the 747 or A380 (or Concorde) would take only a very tiny fraction of a second to travel the length of their body at supersonic speeds. You'd probably need a plane a mile long to experience a proper double boom.

"Since all the sounds you'd ever hear from the airplane arrive at the same time, the result is a very loud boom (all the 10 seconds or more of sound added together)." When the aircraft moves in air, it disturbs it, pressure will re-equalize, but if the aircraft is supersonic, air cannot move faster than "the speed of sound", so a huge pressure differential forms, propagated away at sound speed. If it reaches our ears before equalization, we first perceive the diluted front pressure, then the abrupt change as the differential passes. It works the same with a totally silent aircraft.

There is always a disruption (i.e a perturbation) in the air by a object traveling through it. Each one can be seen as a sphere (or circle in a 2D diagram). At speeds below Mach 1, these disruptions never converge, i.e. the spheres never meet. However, at any speed beyond Mach 1, they no longer travel faster than the aircraft and get 'left behind'. In this case the sides of each expanding sphere converge along a cone shape into a powerful shock wave that we perceive with as a bang.

 Source
The only difference is that as the aircraft becomes faster, the angle of the sonic boom in regard to the direction vector of the aircraft decreases: The cone becomes more acute as the spacing between each imaginary sphere becomes greater. You can never generate more than than one sonic boom, since it's a one-time transition. (On a more complicated note, some vehicles, included the space shuttle, pull of two sonic booms by disrupting the air twice)
You would perceive the same thing with a boat- above a certain speed you would generate a wake going outwards in two directions to the side behind you.

"Fjordn surface wave boat" by Edmont - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons


text:
What is the blue range indicating on this manifold pressure gauge?
This is baffling me. Does anybody with experience with this type of indicator have any idea what the blue range of this gauge means?

It's mounted in a mock-up panel. I know nothing about where it originally came from, though it seems pretty clear that it's from a turbocharged piston twin.

It's a manifold pressure limit with altitude.  It relates to a limitation on the differential between ambient and total manifold pressure at different altitudes with turbocharged or supercharged engines; a limit on the amount of actual boost with altitude in other words, not the total pressure.
At 30000 ft, standard atmospheric pressure is only just under 9 inches.  20 inches on the gauge is 11 inches of boost above atmospheric.
At 20000 ft, atmospheric pressure is just under 14 inches, and you're limited to 35 inches, which is about 21 inches of boost.
Between 16000 ft and sea level, with atmospheric pressure between roughly 16 and 30 inches, the limitation is the red line of 40, which is anywhere from 10 to 24 inches of boost above atmospheric.
The increasing limitation in maximum boost with altitude is usually related to the reduced cylinder cooling ability of the thinning air with altitude, and the potential for detonation.

The blue scale indicates the maximum manifold pressure (MP) at a given altitude.

from sea level (SL) to 16000 ft: the maximum MP is 40 inHg (inches of mercury).
from 16000 ft to 30000 ft, the maximum MP goes down to 20 inHg.

The altitudes are barometric altitudes.

Do you have a reference such as a POH that describes this? What type have you seen this in?

@Pugz, no, unfortunately not, but it is written on the gauge itself.

So this is indicating the maximum possible given existing atmosphere at a given altitude, not any sort of limit, but just for pilot reference to to compare to the altimeter?


text:
When to reduce power on takeoff (Cessna 182 or similar)?
There are two sides I've heard when taking off in a Cessna 182 or other small airplane with a normally aspirated engine driving a constant speed propeller:

As soon as your wheels are off the ground... Or,
When you're 700-1,000 feet off the ground...

Reduce to about 23" of manifold pressure and then reduce the RPM to 2,450 (or 2,300) depending on the plane.

The POH or Owner's Manual (in my case a 1972 Cessna 182P) simply says Full Power under the Normal Take-Off procedure.
The reasoning I've heard is to try not to over-stress the engine (whatever that means exactly), but on the flip side, I've heard that if an engine is going to do something funky, it's probably going to happen when you do a power reduction, or otherwise do something.
I personally want all the power I can have until I'm far enough off the ground to have options if the engine quits or sputters (turn back if high enough, or glide to a suitable spot if not).
I'm asking is there an "official procedure" as to when you should perform this power reduction (inches off the ground or 700-1,000 feet), and if so, have there been actual studies that say why one way is better than the other, or is this one of those groundless, "endless debates" that are so prevalent in aviation?

The "official procedure" is the one dictated in your aircraft's POH/AFM.
Within the leeway that document gives you (and many of them give you a lot of leeway) this is definitely one of those "endless debate" subjects.

Personally in a single-engine piston aircraft unless the POH directs otherwise or operational considerations (like an altitude restriction from ATC) require something different I would maintain full power (and all other takeoff settings - fuel pumps, etc.) until reaching 1000-1500 feet AGL (depending on what the terrain and obstacles in the area are like), then configure the aircraft for a reduced-power cruise climb if appropriate.
Whether or not the first power reduction is a time of increased failure is irrelevant to me - I operate on the assumption that the engine can fail at any time, and should the engine fail (for whatever reason) I want adequate distance between myself and the ground to make some decisions, confirm my landing spot, and prepare myself, my passengers, and the aircraft for whatever is going to happen next.
1000 feet AGL is my minimum threshold for that sort of activity. It's possible (maybe even likely) that I'm imposing additional wear on the engine in requiring full power for this long, but if the engine decides to fail on climb-out it's not going to matter how "nice" I was being to it on all my previous flights - the only things that are going to matter are my altitude, airspeed, and landing options, and I'm going to want as much altitude and airspeed as I can get to help maximize my landing options!

There are some conditions where I would reduce power sooner than 1000 feet AGL if necessary - for example, if I can't maintain oil or cylinder head temperatures "in the green" in a full power climb a power reduction (or pitch reduction) to keep those engine parameters happy would be in order.
There are also some aircraft/engines which have a continuous power restriction (Full throttle operation limited to 3 minutes,  maximum continuous power 2400 RPM, or similar admonitions you'd find in your POH). In those cases the restrictions should obviously be observed (the engineers who set the limitations had a good reason for doing so), and observing those requirements may necessitate a power reduction or other configuration changes prior to reaching 1000 feet AGL.

Finally, I'm not sure what kind of engine is in your hypothetical Cessna but as an additional point of reference Lycoming has this to say about takeoff operations:

Operating Your Lycoming Engines At Takeoff And Climb
Because there are
  a wide variety of Lycoming engines in operation, the paragraphs below
  may be helpful in understanding the different modes of operation
  required when operating each type at takeoff and climb power settings.
  The Pilots Operating Handbook for the aircraft in which the engines
  are installed should be the final authority as to how the engine
  should be operated.
DIRECT DRIVE ENGINES
Most normally aspirated
  engines are rated at full power for takeoff and climb indefinitely,
  provided engine temperatures and pressures are within the green arc
  area of the engine instruments. Extra fuel, sensible airspeed, and
  cowl flaps, if available, are all helpful in keeping cylinder head
  temperatures within desired limits during takeoff or climb.
  Climb
  requirements may vary; as an example, on a warm day with the airplane
  close to gross weight, and a direct drive engine with a fixed pitch
  prop, the pilot will need full throttle all the way to cruise
  altitude. The same airplane on a cold day and lightly loaded may not
  require full power for climb. After full throttle at takeoff, the
  pilot may want to reduce power 100 or 200 RPM and still not see
  performance suffer. Those direct drive normally aspirated engines with
  a prop governor are also rated indefinitely at full power, and the
  manuals all recommend full power for takeoff, but specify a small
  reduction in power, generally to 85% power climb. Study the specific
  airplane Pilot's Operating Handbook for detailed power settings.

(They go on to talk about geared engines and turbocharged/supercharged engines, but your question was about normally-aspirated engines. This is from Lycoming Flyer "Key Reprints" - I grabbed it here but you can Google it up pretty easily, and I imagine Continental has analogous guidance somewhere.)

Noise abatement procedures may also affect your takeoff and climb power.

Also, for FAR Part 25 aircraft (and I think 23 but am not sure), takeoff power may be maintained for five minutes from the time that the throttle is advanced

@Lnafziger Yup - that's another example of operational considerations. Santa Monica (KSMO) having some of the most publicized "strange" noise abatement procedures.

Yeah, and Teterboro is the #2 crazy/psycho noise airport in the country.  Speaking of SMO though, Falcon even developed a special procedure for their jets designed just to operate out of there without ringing the noise bells, along with a special (lower) maximum takeoff weight.

Great answer, thanks. I especially like your point that you "operate on the assumption that the engine can fail at any time." Further research lead me to this quote by Kas Thomas from his great book "Fly the Engine": "[reducing the power] doesn’t actually hurt anything, either. Unless your engine has a 5-minute power limitation, you can safely operate at full throttle all day long. Many jump planes, banner tugs, and towplanes do just that."
Excerpt From: Kas Thomas. “Fly the Engine.” iBooks. https://itun.es/us/esgqC.l

To add to voretaq7's answer: In addition to the desire to gain as much altitude as quickly possible, there is the following consideration: most engine failures happen when the power configuration is changed (a lot of oil is moving through the hub to adjust the rpm, for example), so changing the power should be delayed until you have gained enough altitude for a safe emergency landing (in real life this might not be possible, of course). Thus your second scenario is preferable under normal circumstances.

'most engine failures happen when the power configuration is changed"  I've heard this for years but nobody can point to statistics or a study of the problem to verify this.   If you have the data to back this up please point us to it.  Thanks!

This is a very good point. I have not seen the statistics myself but the argument above seemed well reasoned when it was presented to me so I am repeating it here. I can also imagine such statistics would be hard to collect with most such incidents resulting in very unintentional landings and what not.

Generally I would ease power back at circuit altitude, trim and then if a climb was required, then I would climb at cruise revs.

I own a Cessna 182P from 1973... POH says full power until all obstacle are clear, then 23MP/2450RPM and keep full reach mixture... Its a little tricky how to read this... Its also confusing all the information (and rumors) you see out there about the engine failing because some power setting change are made. NOT true. Keep you engine in the best shape possible, proper maintencance and forget about when is going to fail. You will beat the lottery first!
The real point is determine when your are clear of obstacles. Maybe your are clear at just 50 feet, or 200 feet. Will you change your power setting at that little altitude?. Sure not. At that point your are dealing with to many other issues, like making wind corrections, or fighting the usual turbulence when leaving the ground effect, and the most important: looking the engine gauges for any trouble, etc.
However, this MUST be a simple point. So, I use a method of correlation between "Clear of Obstacle" from the POH with the runway I am departing from. Once I pass the point of not return back to the runway in case of an engine failure, I start the procedure of re-configuration of power settings to 23/2450RPM...
Simple as that. Lower the nose a little bit before changing power settings and then execute it gently. The full power is the most critical phase for the engine, don't over extended it with no reason!


text:
What is the maximum speed for regulation of sonic boom noise?
If fuel cost and fuel efficiency were not the issue, what is the maximum speed (air speed and ground speed) that business jets or airliners could travel at without exceeding the maximum noise and sonic boom allowed or as regulated in the USA, Europe and the rest of the world.  I need to know why there are no faster business jets and for business class airliners given that private and business fliers are prepared to pay a premium

...mach 1? There is no fixed ground speed, since that depends on the wind.

related, if not duplicate: https://aviation.stackexchange.com/q/11936/1467 & https://aviation.stackexchange.com/q/3748/1467
" I need to know why there are no faster business jets" you can't avoid efficiency if you want to know that.

"[...] given that private and business fliers are prepared to pay a premium" Where did you come to that conclusion? I'm sure that it is quite the opposite, nobody is going to pay a premium to shave 5-10 minutes off a short trip, and maybe 30 minutes off of an international trip. ATC can eat up or make those kinds of savings...

@RonBeyer for "given" read "supposing".

I first thought the proper answer should be: Glacial speed. It will take ages for a government bureaucracy to come up with new regulations.

Business jets are developed to different rules than airliners. The biggest difference is that, indeed, fuel price and fuel efficiency are not an issue when what counts are bragging rights for the fastest plane on the ramp. Their speed has steadily increased and is now at Mach 0.935 for the fastest models. Compare that to Mach 0.78 to 0.85 for regular airliners.
Supersonic business jets were proposed several times in the last decades, but so far nobody has risked to spend the money it needs to bring one design to a type certificate.
Since supersonic flight over land is heavily restricted, the fastest speed would be Mach 0.99. However, since the speed of sound decreases with increasing altitude in parallel with air temperature, what is Mach 1.15 in 40.000 ft becomes only Mach 0.998 on the ground, so the shock will disappear close to the ground. If the goal is to avoid the shock on the ground, flight speed high up can very well be mildly supersonic. However, this will place the airplane close to its drag maximum, giving it exquisitely poor efficiency for a small gain in speed.

Shock will disappear??

@Abdullah Yes, the sharp, N-shaped pressure profile will dissipate and be stretched out once the speed of sound is higher than the speed of the wavefront.

I thought it would just be refracted and would accelerate

@Abdullah But not down, only up. As long as the speed of sound is faster than the source of the noise, what reaches the ground is persistent subsonic noise, no sonic boom. But it needs some distance to dissipate enough. The example with Mach 0.998 on the ground will still be rather loud and concentrated.

So it has to do with the difference between shockwave and sound wave?

@Abdullah The shockwave is a soundwave. Soundwaves are tiny pressure variations, and so are shockwaves.

True Air Speed limit is Mach 1. Ground speed is not relevant to this question.
The reason there are currently no flying supersonic business aircraft is that designing and building an aircraft capable of supersonic flight is very expensive and technically challenging.

Mach 1 is a Mach limit. Since speed of sound depends on temperature, the true air speed limit varies with altitude.

Mach 1 is expressed in knots in aviation and that number is adjusted for altitude. Mach numbers are constants. So to avoid noise restrictions you have to fly at or below Mach 1, which can be any range of speeds depending on your altitude. So, your True Air Speed has to be below that of Mach 1 at the altitude you are flying. That's why I refer to it as the limit, because just saying you have to fly below Mach 1 doesn't really mean anything in and of itself.

It is 0.99 Mach over land.  I don't see any restrictions over the ocean.  Based on the top answer to this aviation SE question, I think if you can design a more stealthy hypersonic transport aircraft and fly it at high enough altitudes in the stratosphere, you may minimize the sonic boom to the extent that it is a non-issue.  The NASA graph in the answer shows that the XR-71 has an insignificant sonic boom when cruising at 60,000 ft MSL compared to the Concord SST.
Ram-jet technology would eliminate the need for the turbine compressor used on current jet engines thus allowing the aircraft to be quieter and more streamlined and stealthier.


text:
How did this incident report detailing a flight taking off and landing at Glasgow result in safety changes at a distant airport?
While reading this report detailing a tire failure and actions taken, I noticed a peculiarity: The flight took off and landed at Glasgow without continuing to Malta (its intended destination) yet the Actions taken says:

For flights from Malta, takeoffs to be carried out with flaps 5 only.

How would the operator find an issue with flights out of Malta for a flight intended to land in Malta, that never did (by virtue of returning to Glasgow)? Is it policy or practice to check all aspects of the flight including those that were not reached due to the incident? Was something not mentioned likely to have been found at Malta (perhaps damage from a previous takeoff)?

The incident was caused by tyre wear. Presumably, the change to procedures at Malta is to decrease tyre wear to make recurrence less likely.

The precise truth cannot be known without consulting the authors of the report.  However, assuming it was not a typo, there are several contributing factors that may lead to this result.
Primarily, aviation is a very conservative business, and every opportunity to mitigate risk will be taken.
In this instance, not only did the aircraft lose a tire, the tire also damaged the hydraulic "A" line, and the flaps.
The main issue to address was the tires themselves, but it was noted that the tire blowout appeared to occur at "rotation", which puts the greatest stress on the main gear tires.
While the airplane may be about to take wing and unload the landing gear, the moment the aircraft's nose rotates up is the moment of peak main gear loading.  The weight of the aircraft is no longer supported by the nose gear, and not yet supported by the wings.  The elevator pushes the tail and empennage downward in order to raise the nose, which further burdens the main gear.  And during takeoff, the aircraft flaps will be lowered to aid in generating more lift while still at low air speeds, BUT, lowering the flaps aerodynamically causes a nose-down "moment", which makes the elevator's job that much harder, and that additional force is also transferred to the main gear at the moment of "rotation".
A couple ways to help alleviate the burden on the main gear are to not drop flaps as much, and to "rotate" more gradually.  Also, since flaps were damaged in the tire incident, having your flaps tucked up higher puts them less in harm's way of a possible exploding tire.
But why that directive in Malta?
According to the link below, the main runway at Malta Luqa Airport is 11627 feet long (3544m), which is fairly long as runways go, so an aircraft can take its time getting airborne if necessary.
Malta Luqa Airport charts, at SkyVector
It's not the longest runway around, but it's longer than necessary for most commercial aircraft, especially at sea level.  Malta is also a very flat place, with its highest point only 253m above the Mediterranean. (830 feet)  This makes it a reasonable place to use a procedure that would result in a longer take-off roll and more gradual climb (from the less-deployed flaps.)
So there are reasons it would possibly be more doable there than at some other airports.  However, I think the dominant factor is this:

Boeing 737-33A, registration 9H-ADH, is a Maltese registration (as indicated by the 9H, and the aircraft belonged to Air Malta at the time of the incident.

I used the past-tense, since the current ledger of aircraft registered in Malta does not include that aircraft.  In fact it was transferred (sold?) to Air New Zealand in 2008, and is now in Bahrain, to the best of my knowledge.
737 s/n 27459 registration history
While I do suspect there is more to the story details than we are privy to in that one publication, it's my opinion, as a certified aircraft mechanic and persistent internet sleuth, that the change in practice was made as a matter internal to Air Malta operations at their home airfield.
Bonus: A photo of the actual aircraft, after the incident in question, sitting cordoned off, on the ramp at Glasgow International Airport (GLA).  Click the link above the pic for a little more info, and additional resources.
Boeing 737, registration 9H-ADH

Cheers!


text:
How heavy are the folding wingtips of 777x?
To understand the mass penalty that is induced by a folding wingtips, as a first order approximation we can start with just the wingtip's mass without the actuating mechanism.
I could not find the 777x wingtips' mass anywhere. Are they the same as the 747 winglets?


text:
What is the maximum interception angle for ILS when on radar vectoring?
Some time ago when I was designing the approach radar module for the ATC simulator for HCAA, the spec was very clear that the limit had to be placed at 45 degrees. So I took it for granted and I didn't make any research of my own.
But very recently I had a discussion that made me wondering and I couldn't find any online documentation. I found Lnafziger's answer suggesting that

Controllers may issue a heading or a course direct to a fix between the IF and FAF at intercept angles not greater than 30 degrees for both conventional and RNAV instrument approaches

So I guess this is it for FAA airspace. But I would like to know if there are any EASA regulations or ICAO recommendations that impose 45 degrees in Europe.

45 degrees.

8.9.3.6
Aircraft vectored for final approach should be given a heading or a series of headings calculated to close with the final approach track. The final vector shall enable the aircraft to be established in level flight on the final approach track prior to intercepting the specified or nominal glide path if an MLS, ILS or radar approach is to be made, and should provide an intercept angle with the final approach track of 45 degrees or less.

ICAO Doc 4444 (PANS-ATM)
That said, we very often use a 30 degree intercept angle, even if we are allowed to go up to 45 degrees.

For completeness, in the USA it is not always 30 degrees; in fact the maximum is 45 degrees, but only for helicopters. The rules vary based on how far from the approach gate the aircraft will intercept the final approach course. The approach gate is an imaginary point one mile outside of the final approach fix, but at least five miles from the runway threshold. From the 7110.65 5-9-2a:

Distance from interception point to approach gate
Maximum intercept angle

Less than 2 miles, or triple simultaneous approaches in use
20 degrees

2 miles or more
30 degrees (45 for helicopters)


text:
What's the point of having ILS on runway signs?
Runway signs show the ILS category next to the runway designation. But if you flew and didn't drive to the airport, you already know (hopefully). Either way, you are taking off, so you don't really much care. One might say that you will have to land again in case of emergency, but ATC might not give you the same runway. So what's the reason of showing ILS category on runway signs?
Note: I changed "markings" to "signs" in this question since markings are painted on the ground, signs are the red ones I am asking for.

EDIT: The linked question is not exactly the same:
What is the purpose of several mandatory stops (RWY AHEAD) at busy airports?
What are mandatory stops? How are they several? (I never noticed that). I didn't know all these until I asked about the "runway signs". The other question presumes that you are familiar with some terminology. And it doesn't mention ILS.
Also, it looks like a similar case. I vote for reopening.

If the downvoter cares to explain I would really appreciate it.

These markings designate the hold-short point during different runway operations.
Runway hold-short points are marked by white text on a red background. They designate a point which any aircraft must not cross without an explicit clearance from ATC. Note that in the below picture, there are two markings:

Cat II or III ILS is used during low visibility operations. In the case of an auto-land, the autopilot literally lands the plane on the runway. To do this, the aircraft systems need a very precise signal from the ILS antenna. Any aircraft on the ground crossing the line of sight between the ILS antenna and the landing aircraft will interfere the signal, sending the landing plane off course.
When a plane is landing on Cat II or III, other planes on the ground need to stay further back the runway. This has an undesirable side effect - the airport capacity is reduced. If somebody is doing a visual approach on a clear day, you can move a bit closer.
This is what happened to a Singapore Airlines Boeing 777 when it used auto-land without informing ATC. Since no one is aware they're using auto-land, the standard hold-short procedure (rather than the low visibility procedure) applies. They drifted off the runway pretty much like a racecar!

The linked video no longer exists on youtube.

@Jamiec I fixed the link. See also this answer about autoland.


text:
Book recommendations for learning how to fly?
With the success of this question, which asks about good books on aerodynamics, I thought I'd ask another general question regarding books that we can turn into a community wiki.
What are good books to use to learn how to fly?  And yes, I know that, in the end, you'll just need a good instructor.  But there are several books that suppliment a good instructor, or can be used by people who are interested in learning to fly, but perhaps are unable to get an instructor just yet.
Note: I am well aware this is a very general question.  But I would like to have a centralized resource, vetted by users of this stack, that we can point to when someone asks for text resources on learning how to fly.

As you pointed out in your question, no book is a substitute for actual instruction in an aircraft with a flight instructor. That being said, doing your homework and knowing what your instructor is going to expect goes a long way toward completing your training in a timely manner.
The books here are all great reference texts to be combined with a flight instruction curriculum.
FAA Publications / Books for initial training
A surprising number of new student pilots are not aware of the wealth of information the FAA has compiled and published to help people learn to fly. There is a whole series of FAA Handbooks and Manuals that you can take advantage of which are available from the FAA as well as from a variety of publishers like ASA. While all of the regulatory information is geared toward US/FAA regulations much of the technique information, signs & markings, etc. will be universal, in conformance with ICAO rules.
I list a whole bunch of them here, but you can find a wealth of information by googling what you want to do and the words "FAA Handbook".

Books on Flying the aircraft - maneuvers, etc.
Quite simply if it flies the FAA probably has a book about how you should fly it.  These books cover basic flying technique and the maneuvers the FAA expects pilots to be able to demonstrate.
The popular ones include:
The Airplane Flying Handbook (FAA-H-8083-3A)
The Helicopter Flying Handbook (FAA-H-8083-21A)
The Glider Flying Handbook (FAA-H-8083-13A)
The Balloon Flying Handbook (FAA-H-8083-11A)
Books on "essential aviation knowledge" - Airport signs & markings, "rules of the air", etc.
The Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25A) is the starting point here.
The Aeronautical Information Manual (AIM) is another key resource (you will often find this as a combined "FAR/AIM" printed publication).
Books for the more advanced stuff - Instrument ratings and beyond
The Instrument Flying Handbook (FAA-H-8083-15B) and Instrument Procedures Handbook (FAA-H-8083-16) are excellent references for pilots pursuing an instrument rating.

+1, Very comprehensive answer, Well Done.